What should I do if 'Error in callback for watcher 'xxx': 'TypeError: Cannot read property 'yyy' of null' occurs when using vue-router in a Vue application?

Vue is a popular JavaScript framework. By using Vue Router, you can easily implement the routing function of single-page applications. But during the development process, we may encounter "Error in callback for watcher" error.

This error usually means that a certain Vue instance property within the Vue component is empty, causing an error when trying to use the property in the getter/setter function of the property. If you encounter this error, here are some possible solutions:

1. Check the properties inside the Vue component

In the code inside the component, make sure you are not using undefined or null variable. For example, if you set a property but do not give it a default value, make sure you have set it to a valid value before you try to use the property.

2. Check the Vue component life cycle

Check the Vue component life cycle to ensure that the component has been correctly initialized before being destroyed. For example, this error may result if you access an undefined property in a component's lifecycle hook function.

3. Check vue-router in Vue components

If you are using vue-router, make sure you have installed and configured it correctly. This error can be caused if you use a certain property on the vue-router component and the property is not set correctly.

4. Check computed properties in Vue components

If you define a computed property and it uses an undefined variable, this error may result. Make sure that computed properties only use variables that are already defined and have a value.

5. Check dependencies of Vue components

Vue components can declare dependencies in their computed properties, which allows Vue to automatically update computed properties when dependent variables change . This error can occur if you use undefined variables in computed properties.

In general, this error usually occurs somewhere inside the Vue component. If you are unable to determine the source of the error, step through the various parts of the Vue component to find where the error is occurring. Once you find the problem, you can implement appropriate solutions to solve the problem.

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